Monitoring and alarm system

ABSTRACT

An alarm and monitoring system provided with a central console having a bank of relay-actuated light indicators. Associated with each relay is a solid-state control circuit having a pair of normally non-conductive transistors, one of which is coupled by wires to an external, normally-open sensor switch at a remote station, the other being coupled by wires to an external, normally closed sensor switch at the same station. The arrangement is such that when either switch is actuated, a bias is applied to the base of the related transistor through a resistor of relatively high value to render it conductive and thereby energize the associated relay. Because the bias is determined by the voltage drop across the resistor, the relatively low resistance in the wires going to the external switches has no material effect on the operation of the system even though this resistance is in series with the resistor.

Levy

[451 Sept. 5, 1972 MONITORING AND ALARM SYSTEM [72] Inventor: Marvin J.Levy, 2133 Kewood Place, Bellmore, NY. 11710 [22] Filed: Sept. 2, 1970[21] Appl. No.: 68,908

[52] US. Cl ..340/213 R, 317/ 148.5 R, 340/227 R,

. 340/276 [51] Int. Cl. ..G08b 23/00 [58] Field of Search ..340/409, 213R, 176, 248 B,

[56] References Cited UNITED STATES PATENTS 3,212,078 10/1965 Shanahan..340/213 R 3,252,156 5/1966 Muehter ..340/276 3,448,447 6/1969 Tetherow..340/409 3,289,191 11/1966 Schaner ..340/176 3,268,765 8/1966 Randolph..315/209 3,268,881 8/ 1966 Vasel ..340/213 R Primary Examiner-David L.Trafton Attorney-Michael Ebert [57] ABSTRACT An alarm and monitoringsystem provided with a central console having a bank of relay-actuatedlight indicators. Associated with each relay is a solid-state controlcircuit having a pair of normally non-conductive transistors, one ofwhich is coupled by wires to an external, normally-open sensor switch ata remote station, the other being coupled by wires to an external,normally closed sensor switch at the same station. The arrangement issuch that when either switch is actuated, a bias is applied to the baseof the related transistor through a resistor of relatively high value torender it conductive and thereby energize the associated relay. Becausethe bias is determined by the voltage drop across the resistor, therelatively low resistance in the wires going to the external switcheshas no material effect on the operation of the system even though thisresistance is in series with the resistor.

5 Claims, 2 Drawing figures alseslsos PATENTEDsEP 51912 SHEET 1 OF 2PATENTED SEP 5 I972 SHEET 3 BF 2 INVENTOR. MA/ew/v J. Asvy Ame/v0 v 1MONITORING AND ALARM SYSTEM RELATED APPLICATIONS This application isrelated to my copending applications Ser. No. 818,677, filed Apr. 23, 1969, and Ser. No. 827,744, filed May 26, 1969, now US. Pat. No.3,643,244.v

' BACKGROUND OF THE INVENTION I This invention relates generally tomonitoring and alarm systems, and in particular to a system in which theexistence of fire, smoke, an illegal intrusion, or any other abnormalcondition'is sensed at any station ina multiple-station installation toproduce a switching aca similar intruder alarm system, switches areassociated withdoors or windows located at various points ina structure,such that when a door or window is violated, the switch related theretois actuated, the switches being linked by wires to a central alarm box.-

While in prior-art systems of this type, the alarm calls attention to ahazardous condition somewhere in the installation, it does not actuallyidentify the activated detector and hence does not point to the locationof the violation. This is a serious drawback when the installation ismade in a multiple-story building, a large warehouse, or in'any otherelaborate structure, for precious time may be lost in finding the exactsource of the violation.

' To overcome these drawbacks, systems have been proposed in which eachstation or door detector is coupled to an indicator on a centralannunciator board which identifies the activated detector. In suchsystems,

alarm system wherein a plurality of external switching sensors atvarious remote stations, which sensors are I either normally open ornormally closed, are coupled by individual lines to pilot lights orother indicators on a central console so that the existence of anabnormal condition at any station is indicated at the console, and ageneral alarm is given.

More specifically, it is anobject of this invention to provide a systemof the abovev type, in, which the status of each station is indicated ata central console by means of individual light indicators, each operatedby a separate relay, the relay being actuated by'a solid-state controlcircuit connected to an external sensor by a line whose length andresistance have virtually no effect on the behavior of the controlcircuit, whereby the system operates reliably with highly extendedlines.

Also'an object of the invention is to. provide a monitoring system inwhich the lines connecting the external sensors to the central console.operate at low voltage and carry minute electrical currents .and henceoffer no danger to building personnel and constitute no fire hazard. 1

Yet another object of the invention is to provide. an

alarm system of simple, reliable and-efficient design which may bemanufactured at low cost.

' Because the system lends itself to use with switching type sensors ordetectors which are either normally open or, normally closed, the systemis highly versatile and has many practical applications. The sensors maybe made sensitive to fire, smoke, or any other abnormal condition whoseexistence creates an emergency, or

the sensors may be simple switches responsive to an unauthorized entrysuch as at a window or door.

Briefly stated, these objects are accomplished in a system having a bankof relay-actuated light indicators at a central console. Associated witheach relay is a solid-state control circuit having a pair of normallynon-conductive transistors, one of which is coupled by wires to anexternal, normally-open sensor switch at a remote. station, the otherbeing coupled by wires to an external, normally closed sensor switch atthe same stain the circuit. Consequently, the voltage established at theannunciator board may fall below the level necessary to actuate theassociated indicator relay.

.While it is possible to compensate for the effect of line resistance,the resultant arrangement becomes relatively complicated and costly.Moreover, in some situations, particularly where the lines go through anchemicals, the current-carrying lines themselves constitute a possiblehazard, for the current therethrough is relatively heavy and may producesparking at the detector contacts or elsewhere in the line, should therebe a failure in line insulation.

BRIEF DESCRIPTION or TH INvE TIoN In view of theforegoing, it is themain object of this invention to provide an improved monitoring andenvironment which may contain explosive gases or tion. t

The arrangement is such that when either sensor switch is actuated, abias is applied to the related transistor in ,the control circuitthrough a resistor of relatively high ohmic value, to produce a voltagedrop thereacross which renders the transistor conductive and therebyenergizes the associated relay. Because the bias is determined by thevoltage drop across the resistor, the relatively low resistance of thewires going to the external sensor switches, even when of great length,

has no material effect on the operation of the system.

' OUTLINE OF THE DRAWING DESCRIPTIO OF THE INVENTION The GeneralArrangement Referring now to FIG. 1, there is shown a monitoring andalarm system in accordance with the invention, the system beingconstituted by a console located at a central point and operativelylinked to a plurality of stations A, B, C, D, etc., disposed at variousremote points in a warehouse, a factory, or other building havingsensors installed therein to detect a condition or conditionsto bemonitored, such as fire, smoke or illegal entry. I

The purpose of the system is to provide centralized indications of theindividual status of the stations. Each station is provided with anormallyopen switch Sx and a normally closed switch S y. If, forexample, the station is intended to protect a door and an adjacentwindow, a normally-open switch may be so mounted on the door wherebywhen the door is forced open illegally, switch Sx is closed thereby,whereas when the window is opened without authority, normally closedswitch Sy is opened thereby. Because each station has switches Sx and Syit is capable of tying in with any existing type of normally-open ornormally closed sensor.

Console 10 is linked to the various stations by a plurality of lines Wextending between switches Sx and Sy at each station and terminal boards11 and 12. The boards are each provided with a bank of terminal pairs,board 11 functioning in conjunction with the normallyopen switches Sxand board 12 with the normally closed switches Sy.

Switch Sx in the first station A is connected to the first terminal pairNOa in board 11, while switch Sy in the same station is connected to thefirst terminal pair NCa of terminal 1. Corresponding connections aremade for the Sx and Sy switches in the other stations with respect toterminal pairs NOb, NOc, etc., and terminal pairs NCb, NCc, etc.

By way of example only, the terminal boards in FIG. 1 have each beenprovided with seven pairs of terminals. In practice, the system may bemade in any desired capacity (as few as two stations, or as many as 10,50 or even more). Mounted on the front panel of console 10 is a bank oflightbulb indicators La, Lb, Lc, etc., therebeing as many bulbs as thereare station terminal inputs. Housed behind the panel is a buzzer 82which gives-a general alarm when any bulb in the console is activated.In practice, an external alarm may also be provided.

The arrangement is such that when either switch Sx or Sy at any stationis activated, or both of them, this fact is indicated by illumination ofthe corresponding' lamp La, Lb, etc., in the bank thereof, theilluminated I l2-volt D-C supply, one end of each bulb being con-.remain de-energized.

The secondary of transformer 13 is connected to a bridge rectifier andfilter circuit 14 whose l2-volt D-C output appears at terminals DC+ andDC. The l2-volt A-C output of the transformer is directly available atterminals AC, and AC: to operate the buzzer Bz.

A l2-volt battery 15 is provided on a stand-by basis, the battery beingautomatically connected into service in the event of A-C power failureby means of a switchover relay not shown). The charge on the battery maybe maintained by a trickle charger operating on the A- C power line. I v

The lightbulbs La, Lb, Lc, etc., are energized by the nected to terminalDC-. A bank of light-operating relays Ra, Rb, Rc, etc., is provided,there being as many relays as there bulbs and associated stationterminals. Initially, when the main power switch 16 in the primary oftransformer 13 is turned on, all relays Ra, Rb and Re Associatedwith-relay Rais a solid-state control circuit Ca, and similarlyassociated with relays Rb and Re are solid-state control circuits Cb andCc. Each circuit includes a pair of transistors 17 and 18 and a pair ofisolating diodes l9 and 20. The coil of relay Ra is connected throughdiode l9 and the collector-emitter path of transistor 17 between thenegative terminal DC+ of the D-C power supply and the positive terminalDC+ thereof by way of the normally-closed contacts a of a single-pole,double-throw light-test and reset switch 21. The coil of relay Ra issimilarly connected to the DC power supply through-diode 20 andtransistor 18.

The base of transistor 17 and the base of transistor 18 in the controlcircuit are normally unbiased whereby these transistors arevinitially-non-conductive and the associated relays Ra isinitiallyde-energized. The other relays under the control of their respectivecontrol circuits are similarly initially de-eriergized.

When, however, either transistor 17 or 18 is rendered conductive, apathis completed between the coil of relay Ra and the power'supply, and therelay is energized to actuate a ganged set of four single-pole,double-throw switches S1, S2, S3 and S4 whose poles P normally engagefixed contacts a but, when the relay is energized, engage fixed contactsb.

lamp being caused to flash so that its operation is more noticeable.

THE ALARM CIRCUIT system, in one preferred embodiment thereof, -is,

derived from an alternating-current 1 15 volt 60 cycle) power line andis stepped down by a transformer 13 to 12 volts A-C or any other valueappropriate to the components forming the electrical system.

One terminal of the terminal pair NO connected by wires W to thenormally-open external switch Sx at station A, is connected topower-supply terminal DC+. The other terminal of the pair NOa isconnected via resistor 22 to the base of transistor 17. When, therefore,normally-open external switch Sx is caused to close by reason of anabnormal condition sensed at station A, a bias is applied to the baseof. transistor 17 whose value is determined by the voltage drop acrossresistor 22. In

practice, resistor 22 as well as resistor 23 has a high ohmicvalue'(l6,000 ohms) and the resultant bias is sufficient to rendertransistor 17 conductive.

As a consequence, relay Ra is energized, thereby actuating relayswitcheS'Sl to S4. Relay Ra, once momentarily energized, is latched,this being accomplished by A similar action takes place should normallyclosed switch Sy at station A be caused to open by virtue of an abnormalcondition. One terminal of terminal pair NCa associated with switch Syis connected to the DC- terminal, the other terminal going throughcontact b and pole P of relay switch S1 to the base of transistor 18,

therebyputting the base at ground level and cutting off this transistor.

But if normally-closed switchSy is caused to open, this lifts the groundvoltage from the base of transistor 18, and the base is then biased bythe voltage drop produced across resistor 23.connected to the positivesupply DC+, to render transistor 18 conductive and to energize relay Ra.

Relay Ra is latched by relay switch S1, for when this switch is actuatedto cause pole P to' move from contact b to free contact a, groundvoltage remains discon- It is important to note that the bias voltageswhich are applied to the transistors of the control circuits for therelays are produced by a base current flow passing through resistors 22and 23 as well as through the wires going to the external switches Sxand Sy; Since these base currents are extremely small, in the order ofmicroamperes, they do not represent the slightest danger to those whomake accidental contact with these wires, nor are these currents capableof producing hazardous sparks.

Moreover, since the resistance of the bias circuit is determined mainlybe resistors 22 and 23 which have high ohmic values, the overallresistance thereof is not materially affected by the relatively lowresistance of wires W, even if thesewires are of great length. Forexample, while a resistance in the wires in the order of 100 ohms mightbe fatal to the operation of a convennected from the base of transistor18, even if external I switch Sy at station A should re-close.

Thus in the event either normally-openswitch Sx at station A or normallyclosed switch Sy is operated as a result of an abnormal condition, relayRa will be energized and held in this state. This same action will occurshould both external switches be operated.

When relay Ra is energized, bulb La is caused to flash. The reason forthis is that bulb La is connected on one side to the negative terminalDC and on the other side to pole P of relay switch S4 which, when therelay is energized, engages contact a. Contact a of relay switch S4 isconnected through a normally closed switchSS of a flasher relay FR topower-supply terminal DC+, thereby energizing bulb La.

The bulb is caused to turn on and off periodically at a rate determinedby a solid-state relaxation oscillator constituted by transistors 24 and25, resistors 26, 27 and28, and capacitor 29. The R-C time constant ofthis circuit is such as to energize the coil of flasher relay FRconnected in the collector-emitter path of transistor at a desiredflashing rate.

One terminal of the relaxation oscillator circuit is connected to DC-and the other to the b contact of relay switch S3 of relay Ra. Hence,when the relay is energized, the relaxation oscillator proceeds toactuate flasher relay FR periodically, thereby causing flasher switch S5to operate intermittently and making and breaking the power circuit tobulb La.

Buzzer Bz isconnected to A-C terminals AC and AC through a normally-openswitch S6 actuated'by flasher relay FR; hence, as the lights are causedto flash, the buzzer is similarly operated intermittently to produce anaudible alarm calling attention to, an abnormal condition. To test thebuzzer, a switch 30 is provided which, when depressed, applies A-C powerthereto.

To test'the indicator lights and alsoto reset the system, one pressespush button switch 21 which causes the pole P thereof to-engage contactb, thereby connecting the positive terminal DC-lof the supply to thelightbulbs La, Lb and Le through the a contact of switch S4 in the relaybank. When pole P of bush-button switch 21 is lifted from its a contact,this breaks the coil circuit of relays Ra, Rband Rc, thereby resettingviolation.

tional system, it has virtually no effect on the present preferredembodiment of a monitoring and alarm system, it will be understood thatmany changes and modifications may be made thereto without, however,departing from the essential spiritof the invention.

Where the sensors at the stations are not of the type producing a changein state from a normally-open to a normally closed switching condition,but rather give rise to a change in value to adegree-depending on thecondition being detected, the system disclosed herein may be adjusted toaccommodate sensors of this type. For example, if the sensor is, a smokeor fire detector whose quiescent impedance is very high (say 250,000ohms), which is equivalent to an open circuit, but whose impedance whensmoke or fire is detected is markedly reduced (say to 120,000 ohms),this change relay, said circuitincluding a pair of normallynonconductive transistors each of which is coupled to said relay suchthat when either transistor is rendered conductive, current is suppliedto said relay to energize same, thereby to operate the indicator coupledthereto,

.C. a first bias resistor connected at one end to the base of a firstofsaid pair of transistors, and a second bias resistor connected at oneend to the base of the second of said pair of transistors and at theother end to a first source of potential capable 'of biasing said secondtransistor into conduction,

D. and a first normally open sensor switch connected to the other end ofsaid first bias resistor and to said first source of potential, and asecond normally closed sensorswitch connected to the base of said secondof said pair. of transistors and to another source of potential capableof biasing said second of said pair of transistors into a nonconductivestate, whereby closing of said first normally open sensor switch willcause conduction of said first of said pair of transistors, and openingof said second normally closed sensor switch will cause conduction ofsaid second of said pair of transistors. 2. A system'as set forth inclaim 1, further including an alarm buzzer which is activated when anyrelay in v the console is energized.

3. A system as set forth in claim 1, further including a diode in serieswith each transistor-in the control circuit. v

4. A'system as set forth in claim l, further including a flasher circuitcoupled to said relay and activated when

1. An alarm and monitoring system comprising: A. a central consoleprovided with a bank of light indicators and a relay coupled to eachindicator to control the operations thereof, B. a solid-state controlcircuit associated with each relay, said circuit including a pair ofnormally nonconductive transistors each of which is coupled to saidrelay such that when either transistor is rendered conductive, currentis supplied to said relay to energize same, thereby to operate theindicator coupled thereto, C. a first bias resistor connected at one endto the base of a first of said pair of transistors, and a second biasresistor connected at one end to the base of the second of said pair oftransistors and at the other end to a first source of potential capableof biasing said second transistor into conduction, D. and a firstnormally open sensor switch connected to the other end of said firstbias resistor and to said first source of potential, and a secondnormally closed sensor switch connected to the base of said second ofsaid pair of transistors and to another source of potential capable ofbiasing said second of said pair of transistors into a nonconductivestate, whereby closing of said first normally open sensor switch willcause conduction of said first of said pair of transistors, and openingof said second normally closed sensor switch will cause conduction ofsaid second of said pair of transistors.
 2. A system as set forth inclaim 1, further including an alarm buzzer which is activated when anyrelay in the console is energized.
 3. A system as set forth in claim 1,further including a diode in series with each transistor in the controlcircuit.
 4. A system as set forth in claim 1, further including aflasher circuit coupled to said relay and activated when the relay isenergized to periodically interrupt current flow to said lightindicator.
 5. A system as set forth in claim 1, further includingholding circuits for said relays to maintain them operative subsequentto a momentary actuation of the associated sensors.